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GHSA-96HG-7P79-GGX2

Vulnerability from github – Published: 2026-05-28 12:30 – Updated: 2026-09-08 09:35
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

xfrm: defensively unhash xfrm_state lists in __xfrm_state_delete

KASAN reproduces a slab-use-after-free in __xfrm_state_delete()'s hlist_del_rcu calls under syzkaller load on linux-6.12.y stable (reproduced on 6.12.47, also reachable via the same code path on torvalds/master and on the ipsec tree). Nine unique signatures cluster in the xfrm_state lifecycle, the load-bearing one being:

BUG: KASAN: slab-use-after-free in __hlist_del include/linux/list.h:990 [inline] BUG: KASAN: slab-use-after-free in hlist_del_rcu include/linux/rculist.h:516 [inline] BUG: KASAN: slab-use-after-free in __xfrm_state_delete net/xfrm/xfrm_state.c Write of size 8 at addr ffff8881198bcb70 by task kworker/u8:9/435

Workqueue: netns cleanup_net Call Trace: __hlist_del / hlist_del_rcu __xfrm_state_delete xfrm_state_delete xfrm_state_flush xfrm_state_fini ops_exit_list cleanup_net

The other observed signatures hit the same slab object from __xfrm_state_lookup, xfrm_alloc_spi, __xfrm_state_insert and an OOB write variant of __xfrm_state_delete, all on the byseq/byspi hash chains.

__xfrm_state_delete() guards its byseq and byspi unhashes with value-based predicates:

if (x->km.seq)
    hlist_del_rcu(&x->byseq);
if (x->id.spi)
    hlist_del_rcu(&x->byspi);

while everywhere else in the file (e.g. state_cache, state_cache_input) the safer hlist_unhashed() check is used. xfrm_alloc_spi() sets x->id.spi = newspi inside xfrm_state_lock and then immediately inserts into byspi, but a path that observes x->id.spi != 0 outside of xfrm_state_lock can still skip-or-hit the byspi unhash inconsistently with whether x is actually on the list. The same holds for x->km.seq versus byseq, and the bydst/bysrc unhashes have no predicate at all, so a second __xfrm_state_delete() on the same object writes through LIST_POISON pprev.

The defensive change here:

  • Use hlist_del_init_rcu() instead of hlist_del_rcu() on bydst, bysrc, byseq and byspi so a second deletion is a no-op rather than a write through LIST_POISON pprev. The byseq/byspi nodes are already initialised in xfrm_state_alloc().
  • Test hlist_unhashed() rather than the value predicate for byseq/byspi, so the unhash decision tracks list state rather than mutable scalar fields.

Empirical verification: applied this patch on top of v6.12.47, rebuilt, and re-ran the same syzkaller harness for 1h16m on a previously-crashy configuration that produced ~100 hits each of slab-use-after-free Read in xfrm_alloc_spi / Read in __xfrm_state_lookup / Write in __xfrm_state_delete. After the patch, 7.1M execs across 32 VMs at ~1550 exec/sec produced zero xfrm_state UAF/OOB hits. /proc/slabinfo confirms the xfrm_state slab is actively allocated and freed during the run (~143 KiB resident), so the fuzzer is still exercising those code paths -- they just no longer crash.

Reproduction:

  • Linux 6.12.47 x86_64 + KASAN_GENERIC + KASAN_INLINE + KCOV
  • syzkaller @ 746545b8b1e4c3a128db8652b340d3df90ce61db
  • 32 QEMU/KVM VMs x 2 vCPU on AWS c5.metal bare metal
  • 9 unique signatures collected in ~9h, all within xfrm_state lifecycle
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-46116"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-416",
      "CWE-763"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-28T10:16:27Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: defensively unhash xfrm_state lists in __xfrm_state_delete\n\nKASAN reproduces a slab-use-after-free in __xfrm_state_delete()\u0027s\nhlist_del_rcu calls under syzkaller load on linux-6.12.y stable\n(reproduced on 6.12.47, also reachable via the same code path on\ntorvalds/master and on the ipsec tree). Nine unique signatures cluster\nin the xfrm_state lifecycle, the load-bearing one being:\n\n  BUG: KASAN: slab-use-after-free in __hlist_del include/linux/list.h:990 [inline]\n  BUG: KASAN: slab-use-after-free in hlist_del_rcu include/linux/rculist.h:516 [inline]\n  BUG: KASAN: slab-use-after-free in __xfrm_state_delete net/xfrm/xfrm_state.c\n  Write of size 8 at addr ffff8881198bcb70 by task kworker/u8:9/435\n\n  Workqueue: netns cleanup_net\n  Call Trace:\n   __hlist_del / hlist_del_rcu\n   __xfrm_state_delete\n   xfrm_state_delete\n   xfrm_state_flush\n   xfrm_state_fini\n   ops_exit_list\n   cleanup_net\n\nThe other observed signatures hit the same slab object from\n__xfrm_state_lookup, xfrm_alloc_spi, __xfrm_state_insert and an OOB\nwrite variant of __xfrm_state_delete, all on the byseq/byspi\nhash chains.\n\n__xfrm_state_delete() guards its byseq and byspi unhashes with\nvalue-based predicates:\n\n\tif (x-\u003ekm.seq)\n\t\thlist_del_rcu(\u0026x-\u003ebyseq);\n\tif (x-\u003eid.spi)\n\t\thlist_del_rcu(\u0026x-\u003ebyspi);\n\nwhile everywhere else in the file (e.g. state_cache, state_cache_input)\nthe safer hlist_unhashed() check is used. xfrm_alloc_spi() sets\nx-\u003eid.spi = newspi inside xfrm_state_lock and then immediately inserts\ninto byspi, but a path that observes x-\u003eid.spi != 0 outside of\nxfrm_state_lock can still skip-or-hit the byspi unhash inconsistently\nwith whether x is actually on the list. The same holds for x-\u003ekm.seq\nversus byseq, and the bydst/bysrc unhashes have no predicate at all,\nso a second __xfrm_state_delete() on the same object writes through\nLIST_POISON pprev.\n\nThe defensive change here:\n\n  - Use hlist_del_init_rcu() instead of hlist_del_rcu() on bydst,\n    bysrc, byseq and byspi so a second deletion is a no-op rather\n    than a write through LIST_POISON pprev. The byseq/byspi nodes\n    are already initialised in xfrm_state_alloc().\n  - Test hlist_unhashed() rather than the value predicate for\n    byseq/byspi, so the unhash decision tracks list state rather than\n    mutable scalar fields.\n\nEmpirical verification: applied this patch on top of v6.12.47, rebuilt,\nand re-ran the same syzkaller harness for 1h16m on a previously-crashy\nconfiguration that produced ~100 hits each of slab-use-after-free\nRead in xfrm_alloc_spi / Read in __xfrm_state_lookup / Write in\n__xfrm_state_delete. After the patch, 7.1M execs across 32 VMs at\n~1550 exec/sec produced zero xfrm_state UAF/OOB hits. /proc/slabinfo\nconfirms the xfrm_state slab is actively allocated and freed during\nthe run (~143 KiB resident), so the fuzzer is still exercising those\ncode paths -- they just no longer crash.\n\nReproduction:\n\n  - Linux 6.12.47 x86_64 + KASAN_GENERIC + KASAN_INLINE + KCOV\n  - syzkaller @ 746545b8b1e4c3a128db8652b340d3df90ce61db\n  - 32 QEMU/KVM VMs x 2 vCPU on AWS c5.metal bare metal\n  - 9 unique signatures collected in ~9h, all within xfrm_state\n    lifecycle",
  "id": "GHSA-96hg-7p79-ggx2",
  "modified": "2026-09-08T09:35:30Z",
  "published": "2026-05-28T12:30:29Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-46116"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:59146"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:59147"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:59148"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:59149"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-46116"
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    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2482523"
    },
    {
      "type": "WEB",
      "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/14acf9652e5690de3c7486c6db5fb8dafd0a32a3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/26edb0a3c99f9d958c212be68b21f1221614dcf0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2c617848ae6e4f07a3e397f604208c293bbecacc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3943fcad7694a7d0b15aeabe7d3cc2a2eb8e92e8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/4980162de555cb838f1a189ce7d2cbf5d2e7b050"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6b4dc3181b4bfc5f5fc33ab33b1dc6e15759f4b6"
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    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a2e2d08fb070fab4947447171f1c4e3ca5a188e5"
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    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b4a53add2fa8f1b5aa17d4c5686c320785fab182"
    },
    {
      "type": "WEB",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-46116.json"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:36018"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:39179"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:39180"
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    {
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      "url": "https://access.redhat.com/errata/RHSA-2026:39371"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:41234"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:41235"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:42919"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:43231"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:44385"
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    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:47632"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:47633"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:47739"
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    {
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      "url": "https://access.redhat.com/errata/RHSA-2026:59143"
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    {
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      "url": "https://access.redhat.com/errata/RHSA-2026:59145"
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  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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